The Cell Signalling Unit is developing new treatments for a range of diseases, such as epilepsy, cancer, kidney disease, and infectious diseases like coronaviruses.
The Cell Signalling Unit studies the detailed molecular mechanisms of how signals are sent from one cell to another in the body, with a focus on developing new treatments for epilepsy and other neurological disorders.
We are also using an understanding of dynamin and other signalling molecules to develop new treatments for a range of diseases, such as cancer, kidney disease, and infectious diseases like coronaviruses.
We have the twin goals of advancing basic science and translating research findings into practice. The basic science focuses on understanding the normal signalling events within cells that allow nerve cells to communicate. Surprisingly, similar mechanisms also control the last stage of the cell division cycle. One way these are connected is called endocytosis – whereby cells internalize signals or nutrients from the outside. Many genes are required for endocytosis, but the master regulator is dynamin. Of the three dynamin proteins in the body, the CSU studies dynamin I (dynl) and dynamin II (dynll). Dynamin continues to reveal multiple functions, and cells have complex mechanisms they use to restrict dynamin’s activity.
We also study proteins that act in endocytosis, including clathrin and syndapin I. Our study of endocytosis has led to the development of small molecules that could potentially treat epilepsy, kidney disease and some infectious diseases. Although early days, this is an ambitious, long-term translational program aimed at capitalizing on our basic science discoveries to ultimately develop new disease treatments.
Understanding how endocytosis occurs and is controlled is now helping us develop potential new therapies to control nerve communication and, hence, control diseases such as epilepsy.”
Head, Cell Signalling Unit and Co-Director of ProCan
Head, Cell Signalling Unit and Co-Director of ProCan
We aim to understand the molecular mechanism of synaptic vesicle endocytosis (SVE), an important method of nerve cell signalling, by understanding how phosphorylation (the addition of a phosphate molecule to a protein) affects larger protein-protein interactions. Dynamin I has two splice variants, long or short. We discovered that the calcineurin protein selectively docks with the dynamin I short splice variant to regulate bulk endocytosis, which is used during periods of intense nerve cell activity, like epileptic seizures.
Phosphorylation of particular sites within dynamin I (called Ser-774 and 778) blocks recruitment of syndapin, but not endophilin, which binds to the same site. We mapped the endophilin-binding sites and, surprisingly, found that dynamin I actually has two endophilin binding sites: a minor binding site at the previously known site, but also a major binding site in a different position in the dynamin I long variant. Each interacts with endophilin independently, yet endophilin can only engage one site at a time. This is important information for designing drugs to selectively interfere with these interactions, which may allow us to more finely tune the treatments we are developing for kidney disease and other conditions.
Since SVE is a calcium-triggered process, we proposed that the fastest route to discovering which proteins are important to this process and how they function is to identify the phosphorylation sites (aka phosphosites) in each of the SVE proteins that rapidly respond to calcium stimulation. So far, we have identified >400 unique phosphosites on over 160 proteins using our novel pull-down procedure to capture the major SVE and related proteins. In addition, we successfully revealed the calcium-sensitive subset of phosphosites. Bioinformatics has helped to reveal exciting new findings, providing us a handle on the different signalling pathways. Furthermore, we completed an extensive analysis of the phosphorylated SVE proteins from cdk5-knockout mice using mass spectrometry. Cdk5 is an important signalling molecule involved in many cellular processes, but has recently been implicated in a range of neurodegenerative diseases like Parkinson’s and Alzheimer’s. We found a subset of proteins that are potential cdk5 substrates, which will help us understand how cdk5 is involved in these disorders and potentially lead to new avenues of treatment.
In order for dynamin to perform its role in endocytosis, it needs to form into a helical structure around the necks of endocytic vesicles, which are basically extensions of the cell membrane. In addition to forming helices, dynamin can also self-assemble into rings that are 40 nanometres in diameter (about 30 molecules) of unknown function. Ring Stabilizer compounds are small molecules that affect dynamin’s activity that we have discovered and patented. These compounds have two unique actions compared with dynamin inhibitors: they stimulate dynamin activity by promoting ring assembly, and they prevent rings from disassembling. This produces prolonged and sustained activation of dynamin. We aim to uncover the cellular mechanisms underlying our novel Ring Stabilizers and develop them as future therapeutics for the treatment of proteinuric kidney diseases.
We have developed a drug discovery program with Professor Adam McCluskey at the University of Newcastle. In collaboration with our research partners, we designed compounds that inhibit dynamin (dynamin inhibitors) and published many new classes which we call the dynoles, the iminochromenes the pthaladyns and the dyngos. Each of these compounds block endocytosis in cells, but we also demonstrated two additional uses. Firstly, they block the uptake of certain viruses into cells, suggesting they may be of future use to treat infectious diseases. Secondly, we showed that they block cell proliferation and cause cell death in human cancer cells. This series of exciting studies demonstrates their potential to be developed into novel anti-cancer drugs in the long term. We look forward to being able to generate many new and more potent dynamin inhibitors, with the hope that we can distinguish between dyn I and dyn II activity to individually target compounds for epilepsy or glioblastoma treatments.
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